The present invention relates to a bicycle hub, and more particularly to a bicycle freehub which can lessen the strong shearing force and torque generated during transmission.
In the known technology of the prior art, the structural elements of a bicycle include a main frame, steering fork, saddle, two wheels and pedals, freewheel, chain, sprocket, and a front and a rear hubs, etc. Human power for driving the bicycle is transmitted through the pedals, chain, sprocket assembly and hubs to the wheels. The front and rear hubs must be made sturdy enough to support the load and absorb any strong vibration and impact during riding.
As shown in FIG. 1, a traditional bicycle rear hub comprises a hub body 200, an axle 300, a sprocket assembly 100, two ball retainers 310, 320, a freewheel 105, a support bearing 130 and two lock cones 330, 340. The axle 300 is coaxially disposed in the hub body 200 which is supported by the two ball retainers 310, 320 on the axle 300. The front part of the sprocket assembly 100 forms into at least one sprocket 103 and the rear end has a connecting ring 120 with a threaded inner wall for connecting the sprocket assembly 100 to an end of the hub body 200. The freewheel 105 is connected to the inner wall of the sprocket assembly 100 and co-ordinates with the support bearing 130 to connect the sprocket assembly 100 to the axle 300 for rotation. At least one ratchet device 110 is installed between the inner wall of the sprocket assembly 100 and outside of the freewheel 105 for providing one-way train drive of a fixed direction and driveless reverse rotation.
Such traditional rear hub of the bicycle has the following disadvantages:
1. When human power is transmitted from the pedals through the sprocket assembly and hubs to the bicycle wheels, a torque is separated from the central line of the hub body due to the cross-sectional thickness of the sprocket assembly. Thus, the hub body and axle are subject to such torque and sheering force exerted through the sprocket assembly. When the ride is rough and exertion of force become uneven, the steel balls in the ball bearings are unevenly compressed and thus easily damaged with time. PA1 2. Because the freewheel is connected to the chain wheel and takes up most of the length of the cross-sectional thickness of the sprocket assembly, a connection sheath is used to connect the sprocket assembly to one side of the hub body. The connection sheath is therefore subject to tremendous torque and possible to break off suddenly when the bicycle is in use resulting in great danger to the cyclist. PA1 3. Because the sprocket assembly is subject to strong shearing force and rubbing against the freewheel, a gap is developed between the sprocket assembly mid freewheel and makes the sprocket assembly sway when the bicycle is in motion. The sway of the sprocket assembly thus exerts a torque on the hub body mid cause the wheels to wobble resulting in deformation or breakage of the wheel. PA1 4. Because the sprocket assembly is apart from the central line of the hub body mid the whole transmission is supported on the two ends of the axle, the ball bearings which are closest to the sprocket assembly are most susceptible and have the shortest life of use. PA1 1. The traditional design of a separate freewheel is eliminated, making the functional position of the sprocket assembly closer to the median line of the hub body thus eliminating the torque that causes damage to the elements in the traditional rear hub. PA1 2. The bearing means between the hub body and axle is moved closer to the rim of the freehub, making more even the weight distribution of the freehub and also providing three sets of bearing means for taking the force when the freehub is engaged in reverse driveless rotation. PA1 3. A movable ratchet is used for facilitation heat treatment for use of aluminum alloy for the freehub.
The present invention of a bicycle freehub provides an improved bicycle freehub that avoids the strong shearing force and torque generated by prior rear hub assembly and achieves the advantages described above.